A digital Television (DTV) transmission system adopting an Advanced Television Systems Committee (ATSC) scheme transmits high quality image to users at a high data rate. However, receiving performance depends on a Doppler transition effect or a multipath signal. Accordingly, the receiving performance is deteriorated since an equalizer of the DTV does not compensate perfectly for the distortion of a channel in a poor channel environment such as an indoor receiving environment or a mobile receiving environment.
A method for reducing the channel distortion to be compensated in the equalizer is proposed, and the method for reducing the channel distortion performs a signal process in a spatial domain as well as in a time domain.
Conventional beam forming technologies are classified into an adapted beam forming method and a switched beam selection method.
The adapted beam forming method calculates weight coefficients for beam forming adaptively and in real time.
The switched beam selection method forms a plurality of beams by using weight coefficients fixed to predetermined directions, and selects and uses a signal having the best receiving performance among a plurality of beams.
Thus, the switched beam selection method is embodied more simply than the adapted beam forming method and is easily applicable to a DTV system.
That is, the switched beam selection method comes into the spotlight, since the method improves the receiving performance through relatively simple method in a receiver of the DTV.
Since a received signal via the switched beam selection system is inputted to the receiver of the DTV after most multipath signals are removed, an equalizer of the receiver of the DTV can compensate for remaining distortion of the received signal easily.
In more details, the beam selection method in the conventional switched beam selection technology calculates a channel impulse response based on each beam output, and then selects a beam having the least number of multipath signals. The multipath signals each has a value higher than a predetermined threshold value.